The present disclosure relates to a gasket and a gasket insertion method for mounting a gasket inside an outer cylinder of a syringe.
Conventional methods for inserting a gasket into an outer cylinder in the process of manufacturing syringes and prefilled syringes include: a method of using a sleeve (mechanical capping), and a method of using a vacuum (vacuum capping). In the method of inserting a gasket in a prefilled syringe by using a sleeve, the gasket is first pushed by an inserter from a base end side and is inserted into the sleeve, and the sleeve is inserted to a predetermined position in an outer cylinder filled with a drug solution. Next, when the sleeve is moved toward the base end with respect to the outer cylinder, the diameter of the gasket is increased due to elastic restoring force, and the outer circumferential section of the gasket thereby comes into close contact with the inner circumferential section of the outer cylinder and the gasket is mounted inside the outer cylinder. An insertion method using such a sleeve is disclosed in JP 3940969 B1, for example.
In recent years, prefilled syringes have come to be used for various drug solutions, and depending on the type of drug solution or the prescription, their use for administering a small amount of drug solution to be used up at one time is on the increase. A technique for enabling a stable gasket insertion method regardless of the type of a syringe container or the conditions for filling a drug solution is desired.